Responding because I too spent a long time trying to hook the car seat latch anchors to the strangely perpendicular (i.e., wrong direction) metal clips in between the top and bottom seat cushions in the X6 just under where the symbol shows. I later figured out these were the WRONG place to connect, which explains why this made no sense that BMW would make it this difficult!

The CORRECT location requires you to go an inch or so lower and to spread overlapping leather on the bottom seat cushion at the seam to reveal the latch point. This spot requires no sweating or cursing whatsoever This spot does not seem tucked in or hidden whatsoever once you spread open the overlapping leather.

There is very little information on this if you search on the internet or look in the manual.